Synthesis, phase composition modification, and optical properties of Ce3+/Tb3+ activated KGdF4 and GdF3 submicrocrystals

Ce3+/Tb3+ co-doped series of samples have been synthesized based on a citric acid assisted hydrothermal method. By controlling the hydrothermal treating time, the samples evolve from the Ce3+/Tb3+ co-doped cubic phase KGdF4 with spherical morphology into the Ce3+/Tb3+ co-doped orthorhombic phase GdF3 with rhombic shape finally. The X-ray diffraction data illustrate the phase composition modification process of the samples. The field emission scanning electron microscopy and the transmission electron microscopy images suggest the transformation in the morphology of final products. The spectra of the energy-dispersive spectroscopy reveal the constituents of the samples. And the selected area electronic diffraction patterns prove the crystalline phases of the samples. Based on previous studies and the experimental data, one possible phase composition modification process has been summarized. The photoluminescence excitation and emission spectra and the luminescent dynamic decay curves demonstrate the variations in optical properties of the Ce3+/Tb3+ co-doped final products.